Parametric study for upgrading petroleum vacuum residue using supercritical m-Xylene and n-Dodecane solvents

The upgrading of petroleum vacuum residue was conducted with activated carbon (AC) based catalysts in sub- and supercritical m-xylene and n-dodecane. The conversion, liquid yield, coke formation, sulfur removal, and the product distribution were evaluated at various reaction conditions; different kinds of AC catalysts, temperatures (350-400°C), H₂ pressures (0.50-3.45 MPa), reaction times (5-30 min), and polar components (H₂O, methanol, and ethanol in solution). The acid-treated bituminous coal derived AC produced the highest liquid yield of 76.0 wt % in supercritical m-xylene and 84.4 wt % in supercritical n-dodecane, while it also obtained the lowest coke formation of 16.3 wt % in supercritical m-xylene and 8.4 wt % in supercritical n-dodecane. When compared to the coconut shell derived AC catalyst, its acid-treated catalyst resulted in higher conversion but lower liquid yield due to the high degree of coke formation. Furthermore, the influence of reaction temperature on the upgrading reaction was more profound in both solvent systems than that of hydrogen pressure and reaction time. Regardless of the type of polar component in solution, reduced liquid yield and increased coke formation were observed. The supercritical solvents led to significant improvement in both conversion and liquid yield, as well as reduced coke generation when compared to the subcritical solvents. While surface acidity was an important factor for conversion, coke formation and liquid yield were significantly affected by the type of AC catalyst and a polar component in solution.